Recent studies suggest that the spatial arrangement of receptors on the cell surface may determine the ability of hormones to act. Furthermore, intracellular processing of receptors, subsequent to hormone binding, may be involved in regulation of cell function despite a wealth of information on luteinizing hormone (LH) binding parameters, relatively little is known of LH receptor distribution and turnover. The goal of the proposed research is to examine the distribution of plasma membrane and intracellualr LH receptors in relation to changes in luteal cell function. The first objective is to determine if changes in the surface arrangement of LH receptors are related to other receptors and to receptor mediated changes in cAMP accumulation and progesterone production. Electron microscopic (EM) analysis will be used to assess the distribution of ferritin-LH labeled receptors on non-dissociated cells and on dissociated cells whose function is modified by "nonreceptor" mechanisms (e.g.; ions, diBcAMP) and by receptor mediated processes (e.g. LH, PGF2Alpha). The relationship between unoccupied and occupied LH receptors and between LH receptors and PGF2Alpha) and prolactin receptors will be evaluated by biochemical and immunocytochemical methods. The second objective is to determine the route (process) of LH receptor turnover. The intracellular location of LH receptor protein in isolated cells will be analyzed, independent of hormone binding, by EM immunocytochemical techniques that involve the use of an LH receptor antiserum. Intracellular LH binding sites will be localized with ferritin-LH. Since LH receptor function is critical for regulation of steroidogensis in vivo, the results of these studies are expected to yield new information on receptor regulation of luteal cell function and, by inference, on the regulation of reproduction and human fertility.